Store-operated calcium entry in vascular endothelial cells is inhibited by cGMP via a protein kinase G-dependent mechanism

Store-operated Ca²⁺ entry in vascular endothelial cells not only serves to refill the intracellular Ca²⁺ stores, but also acts to stimulate the synthesis of nitric oxide, a key vasodilatory factor. In this study, we examined the role of cGMP in regulating the store-operated Ca²⁺ entry in aortic endothelial cells. Cyclopiazonic acid (CPA) and thapsigargin, two selective inhibitors of endoplasmic reticulum Ca²⁺-ATPase, were used to induce store-operated Ca²⁺ entry. 8-Bromo-cGMP, an activator of protein kinase G, inhibited the CPA- or thapsigargin-induced Ca²⁺ entry in a concentration-dependent manner. An inhibitor of protein kinase G, KT5823 (1 ♂) or H-8 (10 μM), abolished the inhibitory action of 8-bromo-cGMP and resumed Ca²⁺ entry. Addition of S-nitroso-N-acetylpenicillamine (a nitric oxide donor) or dipyridamole (a cGMP phosphodiesterase inhibitor) during CPA treatment elevated cellular cGMP levels, stimulated protein kinase G activity, and at the same time reduced Ca²⁺ influx due to CPA. Patch clamp study confirmed the existence of a CPA-activated Ca²⁺-permeable channel sensitive to cGMP inhibition. These results suggest that cGMP via a protein kinase G-dependent mechanism may play a key role in the regulation of the store-operated Ca²⁺ entry in vascular endothelial cells.